The Century Council, an organization that battles underage drinking, collects the one-liners from real-life encounters and turns them into stickers and posters. Your local convenience store can order them free for its walls and counters.

"It's a bit of a light-hearted approach to the problem," says spokeswoman Elizabeth Handler. "We thought this was better than having big warnings all over the place. More than anything else, it gets the merchants' attention. It also puts kids on notice they may be asked for ID."

The council, which is supported by the liquor industry, also supplies serious messages for retailers to display, such as "If you're too young to buy, don't even try."